Condensing steam heated boiler feed water heating system including a condensate operated turbine



Aug. 25, 1959 BURl 2,900,793

- CONDENSING STEAM HEATED BOILER FEED WATER HEATING SYSTEM INCLUDING ACONDENSATE OPERATED TURBINE Filed March 25, 1955 ELECTRIC 26 23 MOTORGENERATOR INVENTOR. A L FEED B u E I.

A TTOR/VEY.

Stars CONDENSING STEAM EEATED BOILER FEED WATER HEATING SYSTEM INCLUDINGA CON- DENSA-TE OPERATED TURBINE I Alfred Buri, Winterthur, Switzerland,assignor to Sulzer Freres, Societe Anonyme, Winterthur, Switzerland, acorporation of Switzerland The present invention relates to a condensingsteam heated feed water heating system including a water turbineoperated by the condensate produced in the feed water heaters of thesystem by condensation of the heating steam. The system is particularlysuitable for power plants operated with steam of supercritical pressure.

In order to obtain a good overall efiiciency in plants of this type, itis desirable to raise the temperature of the feed water to above 572 F.,so'that the pressure of the heating steam for the last preheating stagemust be more than 1400 psi. Because of the greater specific heat of thefeed Water at higher temperatures and because of the reduced heat dropbetween the heating steam and the feed water to be heated, the amount ofheating steam in the last preheating stage maybe as much as 20 percentof the amount of steam produced in the steam generator of the plant.

It is an object of the present invention to solve the problem ofreturning the great amount of heating steam condensate accruing in thefeed Water heaters at extraordinary pressure and temperature conditionsto the high pressure steam plants only piston pumps can be used for thispurpose which, because of the great pressure difference, are expensiveand require much space.

It has been proposed to conduct the heating steam condensate into asuitable stage of the boiler feed pump. Since pumps having a pot-likehousing are generally used for producing high feed water pressures, itis difficult to connect the aforesaid conduits with the pump.

The aforedescribed difficulties are avoided by the system according tothe invention, in which at least the condensate available in therelatively high pressure pre heating stages is expanded for producinguseful power and the expanded condensate is returned to a relatively lowpressure part of the feed water supply system. In order to preventexcessive evaporation during the expansion the condensate is preferablycooled by means of feed water prior to the expansion for powerproduction.

Preferably a Water turbine is interposed in the flow of the bleedersteam condensate, the turbine being connected with and driving a usefulwork machine. An impulse type turbine is especially suitable because ithas a relatively good efficiency over a wide range of load under theprevailing pressures and with the available amounts of water. The sizeof such turbines is very small even if great pressure drops must bedealt with. The system according to the invention, however, does notexclude the use of reaction type turbines. Since the amount of PatentedAug; 25, 1959 available condensate may change, it is of advantage toprovide means for controlling the flow area of the nozzle or jet of theimpulse turbine, these means being actuated according to the amount ofavailable condensate. Such a control may be effected mechanically,electrically, or hydraulically.

. The shaft of the water turbine may be connected with an electricmachine, for example for producing electric current to be transmitted toan electric power system. In addition, the shaft of the water turbinemay be connected with the feed pump of the steam generator of the powerplant in which case the electric machine would be an electric motor forsupplying the difference of power for driving the feed pump which is notproduced by the water turbine.

The water turbine may be connected with a feed water reservoir fordischarging the expanded condensate thereinto. If the feed waterreservoiras is usualis located above the feed pump and if the turbine isconnected with the feed pump, an additional pump is preferably connectedwith and driven by the water turbine, the last mentioned pump being usedfor conveying the expanded condensate into the feed water reservoir.

The novel features which are considered characteristic of the inventionare set forth with particularity in the appended claims. The inventionitself however and additional objects and advantages thereof will bestbe understood from the following description of embodiments thereof whenread in conjunction with the accompanying drawing, the one figure ofwhich diagrammatically illustrates a layout of a plant according to theinvention.

The working medium which has been evaporated and superheated in a steamgenerator 1 is conducted into a high pressure portion 2 of a turbineplant and-if desired, after intermediary superheating-into a low pressure portion 3 of the turbine plant. The turbine drives an electricgenerator 4. The expanded working medium flows into a condenser 5 andmay be pumped therefrom by means of a condensate pump 6 through feedwater preheaters 7 and 8 into a feed water container 9. From the feedwater container 9 the Working medium is returned by means of a'feed pump11 through a conduit 10 and through a number of feed water preheatersnamely through Water preheaters 12 and 13 which are arranged in parallelwith respect to the flow of the feed water, and through feed waterpreheaters 14, 15, and 16 which are arranged in series-to the steamgenerator 1.

. The feed water preheaters are heated by means of bleeder steam takenfrom the turbines. The steam taken from the relatively low pressurestages of the turbines flows through conduits 17 and 18 into the feedwater preheaters 7 and 8, wherefrom the condensate may be conducted intothe condenser through a conduit 19. The highest pressure bleeder steamis flown through a conduit 20 into the feed water preheater 16, and theaccruing condensate may accumulate in a container 21. From the container21 the condensate is conducted through the feed water preheaters 15 and12 into a water turbine 22 for driving a bucket wheel 23. Similarly,steam is bled from the high pressure turbine 2 and flown through aconduit 24 and condensed in the feed water preheater 14, the condensatebeing accumulated in a container 25 and conducted through the feed waterpreheater 13 to the water turbine 22 for driving a bucket wheel 26. Thewater turbine is coupled with a driving motor 27 for the feed pump 11and thus directly transmits the power to the feed pump. The waterturbine 22 also drives a pump 29 by means of a bevel gear transmission28 for pumping the expanded condensate through a conduit 30 into thefeed water container 9. A conduit 31 is pro vided for equalizing thepressure in the steam chambers of-the'water turbine 22-and of the feedwater container 9.

Jet-control needles 32 and 33 are actuated by-means of control gears 34and 35 so that the amount of condensate flowing through thefjets 32 and33 is regulated in dependence on the-quantity of condensate accumulatedin'the containers 25 and 21, respectively, ie in response to the'waterlevel measuring devices 36:and 37, respectively.

Thediameters of the bucket wheels 23 and 26-01: the water turbine are ofdifferent size, in accordance with the different pressures at which thecondensate is admitted to the individual wheels. 'l'f, for instance, ata back pressure of 100 psi. in the feed water container 9, the pressurein the bleeder conduit 20 is about 1775 psi. and the pressure intheconduit 24 is about 570 p.s.i.,-the diameter of the bucket wheel 23 .at3000 rpm. would be only 1' 7% and that of the bucket wheel 26 would beonly 9 This shows that also with great amounts of available condensate,the dimensions of the water turbine are small.

The temperature of'the condensate should be reduced as much as possibleby heat exchange with the feed water, so that only little steam isformed when the condensate is expanded. This is the case, if thetemperature of the condensate leaving the feedwater preheaters 12 and 13is not much higher than the temperature inside of the water turbine,which temperature is equal to the saturation temperature at the pressureprevailing in the feed water container and in the interior of the waterturbine. For this reason, the condensate coming from the container 21must be cooled in two stages, namely in the feed water preheaters 15 and12. If the preheater 15 only were used, the cooling would be'insuflicient. If the preheater 12only were used, the feed water wouldbe too much heated so that it would be difficult to condense the bleedersteam from the conduit 24 in ,theheater 14.

The systemaccording to theinvention is applicable to all types of steampower plants, insofar as they use interstage leak-E steam for operatinga feed water preheater. It is immaterial whether the plants include aforced flow or a natural circulation boiler. It is alsounimportant inhow many parts the turbine plant is subdivided. Indirect or surface heatexchangers will be used as feed .water preheaters. The drawingillustrates thepreheaters only diagrammatically and does not limit theinvention to the use of preheaters of the type shown. An actual powerplant will usually have a considerably greater number of preheaters thanshown in thedrawing.

The water turbine may be provided with a conventional safety regulatorwhich is actuated and closes the nozzles when the number ofrevolutionsof the turbine wheels exceeds a maximum value.

What is claimed is:

1. -A boiler feed water heating system for a steam'power plantcomprising an indirectly condensing steam heated feed water heater, awater turbine connected with said feed water heater for receiving andbeing operated by condensate produced in said feed water heater bycondensation of the heating steam, a-boiler feed .water'conduit,'and apumpconnected with said turbine to bedriven thereby and for receivingWater discharged by said turbine and connected with said feed waterconduitfor discharging the water thereinto.

2. A boiler feed water heating system .for a steam power plantcomprising an indirectly condensing steam heated feed water heater, awater turbine connected-with said feed water heater for receiving andbeing operated by condensate produced in said feed water heater bycondensation of the heating steam, a boiler feed water conduit, saidturbine being connected with said conduit for discharging the condensatethereinto, and :a feed pump interposed in said feed water conduit andconnected with said turbine'to be driven'thereby.

'3. A boiler -feed water heating system for a steam power plantcomprising an indirectly condensing steam heated 'feed water heater, animpulse type water turbine connected with said feed water heater forreceiving and being operated by condensate produced in said feedwaterheater, said turbine being provided with a valve for controlling theflow of condensate into said turbine, and means responsive-to the amountof condensate produced in saidheater, said'last mentioned means 'beingconnected with said valve for actuating said valve in accordance withthe'amount of condensate produced in said heater.

"4. A boiler feed water heating system for a steam power plantcomprising an indirectly condensing steam heated feed water heater,awater turbine connected with said feed water heater for receivingand'beingoperated by *condensateproduced in said feed water heater bycondensation of theheating steam, a boiler feed .water conduit, saidturbine being connected with said conduit for discharging the condensatethereinto, and an electric generator connected with said turbine to bedriven thereby.

References Cited in the file of this patent -UNITED STATES PATENTS1,573,851 Nyft'enegger Feb. 23, 1926 FOREIGN PATENTS 470,033 GermanyJan. 5, 1929 575,404 Germany Apr. 27, 1933

